Misclassification of Hypertension Status According to Office Blood Pressure vs 24-Hour Ambulatory Blood Pressure Monitoring.

Background: Ambulatory blood pressure monitoring (ABPM) is the gold standard for establishing the diagnosis of hypertension yet remains underused in Canada. There remains a scarcity of Canadian data surrounding how commonly misclassification of hypertension phenotypes occurs without regular use of ABPM. Methods: This cross-sectional study included 964 consecutive adult patients referred to the Ottawa Hospital Hypertension Clinic who underwent same-day ABPM and automated office-based blood pressure measurement (AOBPM) between 2019 and 2023. The proportion of hypertension status misclassification was determined by comparing ABPM and AOBPM values. White coat hypertension (if on no antihypertensive medication) or white coat effect (if on antihypertensive medication) was defined as AOBPM ≥140/90 mm Hg but mean 24-hour ABPM <130/80 mm Hg. Masked hypertension (if on no antihypertensive medication) or masked uncontrolled hypertension (if on antihypertensive medication) was defined as AOBPM <140/90 mm Hg but mean 24-hour ABPM ≥130/80 mm Hg. Results: The mean (SD) age was 60 (16) years, and 46% of the patients were female. Among 296 patients with normotension or controlled hypertension based on ABPM, 146 (49%) met criteria for white coat hypertension (n = 21) or white coat effect (n = 125). Among 668 patients with uncontrolled hypertension based on ABPM, 364 (54%) met criteria for masked hypertension (n = 65) or masked uncontrolled hypertension (n = 299). Conclusions: The hypertension status of approximately 50% of patients was misclassified by AOBPM vs ABPM. Broader use of ABPM in Canada will improve hypertension awareness, treatment, and control rates.